Hydrocarbon reaction



July 11, 1944. w. H. sHlFFLER ETAL HYDROCARBON REACT I ON Filed Aug. 50k. 1939v Parentalv July 11,1944 2,353,596

UNITED STATES PATENT ori-ics` nYnaooAanoN REACTION William H. Shiiiier, San Francisco, and Laverne P. Elliott, Berkeley, Calif., assigner: to Standard Oil Company of California, San Francisco.

. Calif., a corporation of Delaware Applicltln llllllt 30, 1939, 821181 N0. 292,878

1 Claim. (CL 260-68340 This invention pertains to the manufacture oils orduring the stabilization of natural gasooi' high antilcnock motor fuel hydrocarbons from line, into liquid hydrocarbons of high antilmock` relatively light paraffin hydrocarbons boiling bevalue with yields approximatingv the theoretical low the range of the usual liquid fuels and, more and a minimum of operating difficulty. particularly, to the utilization of relatively light o Other important objects of the invention will parafiinic hydrocarbons having from three to five be apparent from the following description and carbon atoms per molecule, and especially the the appended claim.

normal paraflin hydrocarbons of this group, to This invention contemplates a process for the produce high antiknock motor fuel hydrocarbons substantially complete utilization of such partherefrom. l aliins as butanes, pentanes and propane for the In the cracking of hydrocarbon oils normally manufacture of high antiknock motor fuel hydrogaseous hydrocarbons are produced which are carbons, and especially for the manufactureof lighter than gasoline and too volatile to be inhigh antiknock motor fuel hydrocarbons suitable eluded therein in more than minor quantities for use in or as aviation gasoline, and while it and which for a number of years were therefore will be described and discussed with particular regarded`as waste products from the cracking reference to the utilization of butanes it is not operation, More recently, however, processes intended to be limited thereto.

have been devised for the utilization of some of In accordance `with the invention a light parthe components of such cracking gases in the aiiinic hydrocarbon, such as normal butane or a manufacture of motor fuel, butthe utilization of mixture of normal and isobutane, is catalytically the paraiilnic components, such as butanes, pendehydrogenated in a dehydrogenating zone to` tanes and propane, and especially the normal produce the corresponding olen or oleiins and paraflins, in the manufacture of high antiknock the oletlns produced are catalytically polymerized motor fuel has met with but little success. On in a polymerization zone to produce oleiinpolypyrolysis at high temperatures they produce an mers which, when hydrogenated, are suitable as aromatic rich naphtha but in yields that are quite components in high antlknock motor fuel. The uneconomical. Thermal processes combining deequilibrium conditions are, however, such that hydrogenation and polymerization have been proit is usually not practical to operate a commerductive of better yields of liquid boiling in the cial dehydrogenation plant under conditions` to motor fuel range but of inferior quality in cera0 convert more than a minor fraction, seldom more tain respects and particularly in antiknock qualthan to 30%, of a paraffin to the correspondity when used in motors operating at the high lng olefin in a single operation and, therefore. temperatures desirable in aviation service. Catathe hydrocarbons leaving the dehydrogenator lytic dehydrogenation followed by catalytic polywill contain a substantial proportion of the origimerization and hydrogenation of the polymers is v nal paramn in admixture with the oleiins prosusceptible of producing desirable liquid hydroduced.. Also, when such a mixture of olefin and carbon fuel components but in yields that are unconverted paraffin is passed through a catastill well below the theoretica1 maximum, based lytic polymerization plant to polymerize the oleon the light paraffin consumed. iin, it is impractical, even withl recycle operation, An Object of the-present invention is therefore to obtain better than 85 to 90% conversion ofthe to provide a process whereby the paramn hydro" olefin to polymers and, therefore, the hydrocarcarbons containing from three to five carbon bon mixture leaving the polymerization zone conatoms per molecule can be converted, with subtains both unreacted paraiiin and some unpolystantially theoretical yield. to liquid hydrocarmerized olefin. i 4 Y y bons having a high antiknock value and suit- If this unreacted parafdn is returned to the deable in other respects fOr use aS Or in the Prephydrogenation plant. as must of course be done aration ofaviation motor fuels. if a substantial portion of the original parailin is Another object of our invention is to provide to be converted to liquid motor fuel, the unpolya process wherein catalytic dehydrogenation, merized olefin admixed with it may be consumed polymerization, hydrogenation and alkylation reso to a substantial extent in side reactions, the prodactions are so combined, positioned and interreucts of which comprise hydrocarbons of one or lated as to convert the light parailin hydrocartwo carbon atoms and of relatively low value tobons containing less than six but more than two gether with traces of gummy or tar-like material carbon atoms per molecule, such as produced that may be deposited in theV dehydrogenation during the cracking or reforming of petroleum 'catalyst andv very ymaterially reduce its eilectivel It is a signiflcantfeature of this invention that -f the mixture of unreacted hydrocarbons comprising unreacted parailln and unpolymerized olefin leaving the polymerization stage is passed toan alkylation zone wherein' the olefin is removed through alkylation of an isoparaiiln prior to retane or propane, or mixtutres of any two or vmore of these light paramns may be treated inra substantially similarmanner to produce high antiknock motor fuels therefrom. As pointed out above, a convenient source of these materials is to be found in the Ca, C4 or Ca cuts from cracking still operation or in the overhead from a natural gasoline stabilizer or an appropriate fraction thereof. While the process will preferably be applied to fractions consisting largely of hydrocarbons containing the same number of carbon atoms, such separation is not absolutely necessary.

turning the unreacted paraffin to the dehydrogenation step. The alkylation reaction is effective to remove substantially all of this olefin, in the production of valuable alkymers, and the unreacted parailln is thus left substantially free of any olefin, and the olefin-free unreacted paraffin is then recycled to the dehydrogenation zone. This is especially desirable, since the recycle of even a small proportion of olefin to the dehydrogenation zone is objectionable because of the,

loss of raw material occasioned, the adverse effect on the equilibrium in the dehydrogenation reaction in the dehydrogenation zone and the tendency to cracking, further dehydrogenation, tar production and catalyst poisoning, as above pointed out. The olefin polymers boiling in the gasoline range have a high antiknock value when used in motors operating at the relatively mild temperatures encountered in ordinary automotive service but lose this value to a very considerable extent when employed in fuels for aviation use at higher engine temperatures. The polymers when hydrogenated may, however, befsatisfactorily used in aviation fuels and it is accordingly contemplated by the present invention that the hydrogen produced in the parailln dehydrogenation step may be employed for hydrogenation oi the olefin polymers produced in the polymerization step thereby giving a product of greater value from the same ultimate raw material. v

'I he process of the present invention thus includes a catalytic dehydrogenation step in which a light paraffin hydrocarbon is catalytically dehydrogenated with the production of the corresponding olenn and free gaseous hydrogen, a cata- Lvtic polymerization step in which a portion of the oleflns so produced are catalytically polymerized-to olefin polymers boiling substantially in the range of aviation motor fuel, a hydrogenation step in -which these oleiln polymers are catalytically hydrogenated -by the hydrogen produced in the parafiln dehydrogenation step and analkylation step in which oleiins remaining unpolymerized in the polymerization step are caused to alkylate an isoparafiln prior to returning the originally undehydrogenated parailln, with which they are mixed, to the dehydrogenation step. By this combination of steps a process results which is complete and effective for the conversion of low boiling parailln hydrocarbons. and particularly normal paraillnhydrocarbons, to liquid motor fuels of high antilmock value without substantial loss of raw material.

This invention may be better understood by reference to the accompanying drawing wherein one specific embodiment exemplifying the invention is schematically shown in the figure. While the invention will be explained in connection with this gure by reference to the utilization of butane, which may be normal or isobutane, or a mixture thereof, for the manufacture of high antiknock motorlfuel hydrocarbons, it is to be In this specific example butane may be introduced through line l to the dehydrogenation plant 2. In this plant butane may be dehydrogenated in any known manner, such as, for example, with the use of catalysts such as chromic oxide, magnesium oxide or zinc oxide supported on activated alumina, usually at relatively low pressures and temperatures of 900 to 1400 F., preferable l000 to 1200 F. Hydrogen removed from the butane in the dehydrogenation plant 2 may be withdrawn through line 3 or passed through line 5 for further use, as explained below. This hydrogen will. of course, be separated from the mixture of butane and butene leaving the dehydrogenator by any well-known means, such as by distillation or absorption. The butene formed in the dehydrogenation plant 2 and unreacted butene may be withdrawn through line 4 and the mixture passed to a polymerization plant l. In this plant butene is polymerized in any known manner, such as .by means of phosphoric acid catalysts at temperatures between about and 450 F. or sulfuric acid at temperatures up to about 200 F., to produce low boiling polymers. These polymers thus obtained are useful as motor fuel, but in order to form high antiknock aviation motor fuels therefrom, it 1s preferred to hydrogenate them, and for this purpose they are passed through line l to a hydrogenation plant il, where the polymers are hydrogenated in any well-known manner as by means of a nickel catalyst under moderate hydrogen pressure or a molybdenum sulfide catalyst at higher pressures. Required hydrogen may o 4be supplied to the hydrogenation zone from 'an outside source through line I, or preferably may be supplied from the dehydrogenation plant 2 through lines 3 and i. Hydrogenated polymers may be withdrawn from theA hydrogenation plant I I through a line 1.

As pointed out above, vit is not found practicable in the commercial operation of polymerization processes to convert all the butene to polymers and for this reason the hydrocarbons leaving the polymerization plant l through line It will always contain some unpolymerized butene aswell as the butane which remained undehydrogenated in plant 2. Under certain conditions it may be desirable to operate the polymerization plant so as to leave more than the `minimum `possible amount-of butenes unpolymerized. For instance, the ratio of normal lto isobutane in a C4 cut is frequently of the order of two to one and it may then be desirable to polymerize only about 50% .of the butene in order to leave sufficient to alkylate all of the isobutane available. It may also be desirable to limit the polymerization of butenes to about 50% since the polymers so producedhave been found to contain a higher proportion ofmaterial boiling in the aviation fuel range and having a higher antiknock value, when hydrogenated, than when higher degrees of polymerization are employed. In any case, the mixture of unreacted clearly understood that normal pentane, isopen- `butane and unpolymerized butene is then passed throughline I toanv alkylation plantr where the unpolymerized butene is used to alkylate isopar'aifin -to` form high antiknock motor fuel' hydrocarbons and is thus separated fromthe unreacted .butana Thus, throughy line Ill-the butane and unpolymerized 'buten'e .from the polymerization plant 8' arerled to an alkylation plant, where they maybe introducedinto the mixing zone l2 thereof. Iso-- butane to be alkylated andan alkylation'catalyst, suchasv sulfuric acid, are also introduced'to the mixing zone I2, and the three Jreactants are thoroughly mixed and agitated to promote the alkylation of the isobutane by the olefin. Additional, or all, the isobutane to'be alkylated may' 15 beV introduced to the mixing zone I2 through `line Il, and the catalyst may be introduced through line Il. The reaction` mixturefrom mixery I2 is discharged through line Ilinto a separating zone.V I8 where the catalyst separates from the hydro` carbonsf. Separated catalyst, indicated by lia, may be withdrawn through line yII or returned through line I8 by pump I9 to the mixingzone I2. Fresh catalyst may be added through line 2l as needed. p

From the upper part o! separating zone ISthe hydrocarbon reaction mix consisting of normal paramn, unreacted isoparain and alkymer product may be .withdrawn through line 2| and passed to alkymer stabilizer 22, wherein the light hydrocarbons, such as normal butane and isobutane, are'removed from the alkymer product. The alkymer product may be withdrawn through line 28 and the desirable componentsthereof used to make motor fuel. The mixture o1' normal butane and isobutane taken overhead from stabilizer 22 through line 24, may be condensed in condenser :land passed to receiver 26. From receiver 28 a portion of the condensed mixture of normal and isobutene may be returned to the stabilizer 22,- while the remainder is'passed through line 21 to a butane still 28 wherein isobutane is taken oil' overhead and the normal butane is withdrawn from the bottom.

The isobutane passing overhead from still 28 may be condensed in condenser 29, collected in receiver I0 and returned to the alkylation zone l2 through lines 32 and I3. 'I'he normal butane, now freeof olefin, is withdrawn from the bottom of still 28 and returned to the dehydrogenation zone 2 through line I5. The mixture of isobutane and. normal butane, or a portion of it, taken ofi! overhead from. stabilizer 22, which is also now free of oleiins, may be returned directly to the dehydrogenation zone 2 through line 34, without separation in still 28, if desired,.depending, of course. to a largefextent upon the availability ofv isobutane and consequently on whether or not it must be conserved for alkylation.

In the alkylationmixing zoner I2 it is desirable to have a highratio of isoparaflin to olefin inV order that the best alkymer product'may'be-pro- 1 ducedin good yield. For desirable operation this ratio should be at least above a molecular ratio of about ten to one and for the best results'the molecular ratio should be as high as about fifty to one or above. In order to obtain this desired high ratio of isoparailln to oleiln inthe mix/ing' zone I2,` isobutane may beadded to the alkylation zoneV from an outside source through line 38, isobutane may be recycledfrom still 28 'through line l 32, or hydrocarbons fromthe upper part of separating zone I6, contalninga substantial quantity ot unreacted isobutane, may be returned throughk line Il by pump 33 to the mixing zone l2, or any 75 to butenein dehydrogenationv plant 2-is usually about 25% to 30% per pass.' and the polymerization ofthe butene in polymerization plant 8 may' be'i'romA about 50 to 90%, as explainedabove', whilethe utilization of butene in the alkylation reaction is substantially complete, the overhead from still 22 seldom containing more than 0.1% olefin. It will thus `be seen that by the foregoing process butane may be converted almost quantitatively to lightv liquid motor fuel of high antiknock value with a considerable saving in raw material, over an operation involving only dehydrogenation and' polymerization, and a worth# while improvementin the cycle of the dehydrogenation catalyst;

Although this invention contemplates any method of polymerization in polymerization plant 8' which produces polymers especially suitable, when hydrogenated. as high antiknock motor fuel components, it is .foundrthat best over-all. results are obtained` when the polymerization is suillciently selective fto remove all of the isobutene that may be present,` since the alkymers produced by alkylating isobutane with the normal butenes insteadof isobutene, areof better quality. especially insofar as antiknock value isconcerned, and usually contain a higher proportion of the lighter components most desirable in vaviation motorfuels. This selective removal'of isobutene phosphoric acid absorbed on a nonporous inert` solid support, such as broken .quartz,.is suitable for thispurpose. TheV selective removal o! `iso butene mayalso'be effected by polymerizing the isobutene to di-isobuteneby either of the above types of phosphoric acid catalyst, maintaining.` the reactionv temperature between about 50 and 150 F., or by liquid sulfuric acid ofabout 60% to '10% H2804 at a temperature between about f and 130 F.

The catalyst for effecting the alkylation'freactionl may be any' catalyst known to be useful for this purpose; however, sulfuric acid of concentration from about to about 98% HaSO`4-at temperatures ranging fromithev melting point of the catalyst when in use to aboutf F; is pre-- ferred. Other alkylation catalysts, suchas `chlorosuli'onic'acid, a mixture-of chlorosulfonic acidy and sulfuric acid, or a mixture of sulfuricv acid` and phosphoric acid may also be used. Such furic acid type.

a strength or an effectiveness which'will produce a satisfactory alkymer product,v some spent catalyst may be withdrawn through line I1 and a corresponding'amount of `fresh catalyst'supplie'd through line 20. y

Having now described and illustrated. the proc-A ess of our invention for the substantially co'mplete conversion of normally-gaseous parafllnsto combinationof these three methods may be used.,A In the operation of the process of the present' invention it is found that the conversionofbutaneV liquid motor fuels of high antiknock value, we

claim:

Process of manufacturing high antiknock mo-` tor fuel hydrocarbons from a mixture of low boiling hydrocarbons containing normal paramns having more than two and less than six carbon atoms per molecule, which` comprises subjecting such parailns to a dehydrogenation stage in which said paramns arepartially dehydrogenated forming oletins, subjecting the resulting mixture oi' parafllns and olefins to a polymerization stage wherein the olefins are partially polymerized. separating the resulting polymers from the remaining mixture o! said paramns and said olens,

subjecting said last-mentioned mixture to an alkylation stage in the presence of isoparamn which is alkylated by said olefins thus freeing said mixture oi substantially all of said olenns so that said 'parafllns contain less than about 0.1% olen, separating normal paramns'therefrom and returning the normal parailins thus separated to said dehydrogenation stage wherein said paramns are further subjected to dehydrogenation, and returningy separated isoparamn t0 said alkylation stage.

wrLLrAM H. smr'rmn. LAVERNE P. muon'. 

